Radiopaque catheters are used to provide visualization of the catheter during a therapeutic procedure such as PTCA or kidney stone removal. Radiopaque catheters are also used in diagnostic imaging procedures for injecting contrast medium into the body of a patient. Several commercially available radiopaque catheters include increased radiopacity about the distal catheter end. Visualization of the distal catheter end is critical for locating the catheter end with respect to anatomical structures and preventing inadvertent trauma or injury of a vessel or duct during advancement of the catheter.
One approach to providing a curved, radiopaque catheter is to form the catheter body from a compound of a polyurethane material with either 20 weight percent of barium sulfate or 33.5 weight percent of bismuth subcarbonate. The distal catheter tip is formed from a compound of a polyurethane material with 49.83 weight percent of bismuth trioxide. As a result, the curved catheter body is slightly radiopaque, and the distal catheter tip is more radiopaque than the curved body.
A problem with this catheter is that the compound material forming the distal catheter tip is only moderately radiopaque in comparison to highly radiopaque materials such as solid platinum, gold, or tungsten. As a result, the radiopacity of the distal catheter tip indicates the general position thereof. However, the position of the curve in the catheter body cannot be readily discerned. Furthermore, the point at which the curved catheter body ends and the distal catheter tip begins has no readily imageable boundary. Another problem with this curved catheter is that visualization of the slightly or moderately radiopaque catheter materials is deemphasized or overcome by the images of surrounding tissues. The problem is compounded when injecting contrast medium into a blood vessel or another duct of a patient's body via the curved catheter. The contrast medium flows into the vessel or duct and surrounds the curve and the distal tip of the catheter. As a result, the curve and the distal tip of the catheter are difficult to discern or are completely obstructed by the bright image of the contrast medium.
Yet another problem with this curved catheter is that safely steering and maneuvering the catheter through tortuous vessels or ducts requires precise visualization of the distal catheter tip. When the precise position of the curve or the distal tip of the catheter is not visible, the catheter can be inadvertently advanced into anatomical structures. As a result, tissue is injured or punctured. When imaging a coronary artery or a ventricle of the heart, such trauma or injury results in serious complications and bleeding.
In view of these problems, an attempt was made to increase the radiopacity of the curved catheter by providing a plastic formulation with a higher than 75 weight percent of a radiopaque agent. This known attempt resulted in failure due to the brittleness of the plastic catheter material. Furthermore, the plastic catheter material exhibited a general loss of the desired softness and flexibility.